The breeding of two polyploid rice lines with the characteristic of polyploid meiosis stability

Polyploidization is a basic feature of plant evolution. Nearly all of the main food, cotton and oil crops are polyploid. When ploidy levels increase, yields double; this phenomenon suggested a new strategy of rice breeding that utilizes wide crosses and polyploidization dual advantages to breed super rice. Because low seed set rates in polyploid rice usually makes it difficult to breed, the selection of Ph-liked gene lines was emphasized. After progenies of indica-japonica were identified and selected, two polyploid lines, PMeS-1 and PMeS-2 with Polyploid Meiosis Stability (PMeS) genes were bred. The procedure included seven steps: selecting parents, crossing or multiple crossing, back-crossing, doubling chromosomes, identifying the polyploid, and choosing plants with high seed set rates that can breed themselves into stable lines. The characteristics of PMeS were determined by observing meiotic behaviors and by cross-identification of seed sets. PMeS-1 and PMeS-2, (japonica rice), have several characteristics different from other polyploid rice lines, including a higher rate of seed set (more than 65%, increasing to more than 70% in their F1 offspring); and stable meiotic behaviors (pairing with bivalents and quarivalents nearly without over-quarivalent in prophase, nearly without lagging chromosomes in metaphase and without micronuclei in anaphase and telophase). The latter was obviously different from control polyploid line Dure-4X, which displayed abnormal meiotic behaviors including a higher rate of multivalents, univalents and trivalents in prophase, lagging chromosomes in metaphase and micronuclei in anaphase and telophase. There were also three differences of the breeding method between PMeS lines and normal diploid lines: chromosomes doubling, polyploidism identifying and higher seed set testing. The selection of PMeS lines is the first step in polyploid rice breeding; their use will advance the progress of polyploid rice breeding, which will in turn offer a new way to breed super rice. Supported by the National Natural Science Foundation of China (Grant Nos. 39970447, 30240090, 30471063 and 30650002), the High Technology Research and Development Program of China (Grant No. SZ-01-02-02), the Chenguang Youth Science and Technology Project of Wuhan City (Grant No. 20045006071-31), and the Educational Commission of Hubei Province of China (Grant No. 2004D004)     

Polymorphic microsatellite markers for chromosomal races of Australian morabine grasshoppers (Vandiemenella,viatica species group)

Chromosomally diverse Australian morabine grasshoppers (genus Vandiemenella, viatica species group) have parapatric distributions and occasionally hybridize at contact zones. To investigate population genetic structure and the extent of gene flow between chromosomal races/species of Vandiemenella, we isolated and characterized nine polymorphic microsatellite loci and one insertion/deletion polymorphic locus. The numbers of alleles per locus ranged from two to 34 across three chromosomal races on Kangaroo Island, South Australia, and expected heterozygosity within races ranged from 0.00 to 0.94. Inter‐taxon amplification was generally successful within Vandiemenella, but not for other morabine genera.     

Statistical optimization of medium components for the production of xylanase byAspergillus niger KK2 in submerged cultivation

Medium composition was optimized for the production of xylanase byAspergillus niger KK2 using statistical experimental designs. Corn steep liquor (CSL) and industrial yeast extract (IYE) were the most important factors affecting xylanase activity. The medium that produced the optimum conditions for the production of xylanase contained 3% rice straw, 1% wheat bran, 6.3% CSL, 0.15% IYE, and 0.5% KH₂PO₄. After 4 days of cultivation under optimized conditions in a 2.5-L stirred tank reactor the activity and productivity of xylanase were 620 IU/mL and 6,458 IU/L.h, respectively. The highest xylanase activity obtained using the optimized medium was 80% greater than the activity obtained using basal medium. The xylanase activity predicted by a polynomial model was 670 IU/ml.     

High-lysine corn generated by endosperm-specific suppression of lysine catabolism using RNAi

Because of the limited lysine content in corn grain, synthetic lysine supplements are added to corn meal-based rations for animal feed. The development of biotechnology, combined with the understanding of plant lysine metabolism, provides an alternative solution for increasing corn lysine content through genetic engineering. Here, we report that by suppressing lysine catabolism, transgenic maize kernels accumulated a significant amount of lysine. This was achieved by RNA interference (RNAi) through the endosperm-specific expression of an inverted-repeat (IR) sequence targeting the maize bifunctional lysine degradation enzyme, lysine-ketoglutarate reductase/saccharopine dehydrogenase (ZLKR/SDH). Although plant-short interfering RNA (siRNA) were reported to lack tissue specificity due to systemic spreading, we confirmed that the suppression of ZLKR/SDH in developing transgenic kernels was restricted to endosperm tissue. Furthermore, results from our cloning and sequencing of siRNA suggested the absence of transitive RNAi. These results support the practical use of RNAi for plant genetic engineering to specifically target gene suppression in desired tissues without eliciting systemic spreading and the transitive nature of plant RNAi silencing.     

Design,Synthesis, and Evaluation of Anti-HBV Activity of Hybrid Molecules of Entecavir and Adefovir: Exomethylene Acycloguanine Nucleosides and Their Monophosphate Derivatives

Exomethylene acycloguanine nucleosides 4, 6 and its monophosphate derivatives 5, 7, and 8 have been synthesized. Mitsunobu-type coupling of 2-N-acetyl-6-O-diphenylcarbamoylguanine (11) with primary alcohols proceeded regioselectively to furnish the desired N⁹-substituted products in moderate yield. Evaluation of 4-8 for anti-HBV activity in HepG2 cells revealed that the phosphonate derivative 8 was found to exhibit moderated activity (EC₅₀ value of 0.29 μM), but cytotoxicity (CC₅₀ value of 39 μM) against the host cells was also observed.     

Photoperiodic growth control in perennial trees

Plants have to cope with changing seasons and adverse environmental conditions. Being sessile, plants have developed elaborate mechanisms for their survival that allow them to sense and adapt to the environment and reproduce successfully. A major adaptive trait for the survival of trees of temperate and boreal forests is the induction of growth cessation in anticipation of winters. In the last few years enormous progress has been made to elucidate the molecular mechanisms underlying SDs induced growth cessation in model perennial tree hybrid aspen (Populus tremula × P. tremuloides). In this review we discuss the molecular mechanism underlying photoperiodic control of growth cessation and adaptive responses.